CEPC IR Design
Sha Bai, Yiwei Wang, Dou Wang, Ming Xiao, Jie Gao
09-24-2013
TLEP and CEPC IR designs meeting
CEPC low power design
• Idea :1 ) reduce operation cost ( reduce AC power )2 ) reduce the Microwave system cost
• Method : reduce the IP βy until reach the low IP βy , the parameters table shows several sub-mm βy , to low beta 350um 。
• Advantages:
1) Radiation power reduce , AC power (offer the Microwave power ) reduce , klystron numbers reduce 。2) Beam power reduce , loss of heat energy of beam in SC cavity reduce, AC power due to refrigerator reduce (Now Ring Higgs Factory power without this part )。3 ) 1)+2) AC power reduced remarkably 。
CEPC design parametersNumber of IPs 1 1 1 1Energy (GeV) 120 120 120 120Circumference (km) 50 50 50 50SR loss/turn (GeV) 2.96 2.96 2.96 2.96Ne/bunch (1012) 0.79 0.38 0.33 0.28Bunch number 22 23 21 19Beam current (mA) 16.9 8.45 6.76 5.07SR power /beam (MW) 50 25 20 15B0 (T) 0.065 0.065 0.065 0.065Bending radius (km) 6.2 6.2 6.2 6.2Momentum compaction (10-4) 0.38 0.38 0.38 0.38IP x/y (m) 0.2/0.001 0.071/0.00048 0.056/0.00042 0.041/0.00035Emittance x/y (nm) 14.6/0.073 9.5/0.035 9.1/0.031 8.9/0.026Transverse IP (um) 54/0.27 25.9/0.13 22.7/0.11 19.2/0.096x/IP 0.103 0.076 0.069 0.06y/IP 0.103 0.103 0.103 0.103VRF (GV) 6 6 6 6f RF (MHz) 704 704 704 704z (mm) 2.2 2.2 2.2 2.2Energy spread (%) 0.13 0.13 0.13 0.13Energy acceptance (%) 5 5 5 5BS (10-4) 13.8 13.8 13.8 13.8n 0.6 0.6 0.6 0.6BS (10-4) 4.3 4.3 4.3 4.3Life time due to beamstrahlung (minute)
30 30 30 30
F (hour glass) 0.68 0.48 0.45 0.41Lmax/IP (1034cm-2s-1) 3.1 2.31 1.97 1.58AC power/two beam (MW) * 286 143 114 86Luminosity gain (%) 49 59 69
*AC power for refrigerator is not included
Design challenge
• The IP β reduce , chromatic effect increase ,the design of Final focus will be more difficult 。
• There is no experience of the IP low β FFS design in Ring collider, refer to the low β IR design in linear collider. But the emittance in Ring is much bigger than in the linear collider, higher order aberrations large, the correction will be more difficult.
Final Focus Design without chromaticity correction
Final Focus Design without chromaticity correction
• For βy*=1mm , IR final focus design:– – Vacuum chamber size : H=48mm, V=9.4mm– Quadrupole parameters
x,max=570m, y,max=4400m
Length (m)
strength (T/m)
Aperture (mm) Pole strength (T)
QD1 2.25 132 50 6.6QF2 1.5 104 50 5.2QD3 1.5 7.4 50 0.37QF4 1.5 24 50 1.2
Final Focus Design without chromaticity correction
L* (m) 1.5 1.5 1.5 1.5
IP x/y (m) 0.2/0.001 0.071/0.00048 0.056/0.00042
0.041/0.00035
Emittance x/y (nm) 14.6/0.073 9.5/0.035 9.1/0.031 8.9/0.026Transverse IP (um)(linear)
54/0.27 25.9/0.13 22.6/0.11 19.2/0.096
Transverse IP (um)(estimated)
-/0.59 -/0.542 -/0.542 -/0.540
Transverse IP (um)(simulation)
55.0/0.93
AberrationContribution to beam size(m^2)
R33 2.51E-14R34 4.79E-14T336 5.15E-13T346 2.71E-13
• For βy*=1mm , IR final focus simple design:– σy*/σy*linear = 3.4– Remarkable Chromatic effect– For sub-mm βy* final focus , chromatic effect is more remarkable , correct
ion necessary.
Local-compact FFS designL*=3.5m
Local-compact final focus design
• βy* much similar to the ILC IR design , first we tried the local chromaticity correction scheme (ILC type final focus)
CEPC CEPC CEPC CEPCILC 500GeV base
line
L* (m) 3.5 3.5 3.5 3.5 3.5
IP x/y (m) 0.2/0.0010.071/0.0004
80.056/0.00042
0.041/0.00035
0.011/0.00048
Emittance x/y (nm) 14.6/0.073 9.5/0.035 9.1/0.031 8.9/0.026 0.02/0.00008
Energy spread (%) 0.13 0.13 0.13 0.13 0.124/0.070(e-/e+)
z (mm) 2.2 2.2 2.2 2.2 0.3
Transverse IP (um)
54/0.27 25.9/0.13 22.7/0.11 19.2/0.096 0.474/0.006
Lmax/IP (1034cm-2s-1) 3.1 2.31 1.97 1.58 1.8
CEPC Final focus lattice Design• βy* =0.35mm ( 15MW ) design:
• ILC type Final focus
•
• Vacuum chamber size : H=190mm, V=23mm
• Quadrupole parameters
CEPC
L* (m) 3.51
IP x/y (m) 0.041/0.00035
Dx’ 0.0082
Emittance x/y (nm) 8.9/0.026Energy spread (%) 0.13z (mm) 2.2Transverse IP (um)
19.2/0.096
Lmax/IP (1034cm-2s-1) 1.58
x,max=10000m, y,max=50000m
Length (m) strength (T/m) Aperture (mm) Pole strength (T)
QD0 2.2 0.15 190 11.5QF1 2.0 0.07 190 5.48
Chromaticity correction
• Due to the emittance much larger than ILC, high order aberration increase. T126, T122, T166, T346 and T324 are no longer the biggest ones to be corrected.
• Sextupoles strength optimization, reduce the aberrations.
• σy*/σy*linear = 15, far away from the aim, need optimization.
• σx* increase.
L* (m) 3.5IP x/y (m) 0.041/0.00035Emittance x/y (nm) 8.9/0.026Transverse IP (um)(linear)
19.2/0.096
Transverse IP (um)(no correction; estimated)
-/1.25
Transverse IP (um)(no correction; simulation)
45.8/2.03
Transverse IP (um)(with correction; simulation)
59.8/1.33
Chromaticity correction• Reducing the emittance makes final focus correction easier, but b
eam lifetime and luminosity will be reduced too.• Keep the emittance
• Reduce the L* to make
the chromaticity smaller
Number of IPs 1 1 1 1 1
Energy (GeV) 120 120 120 120 120
Circumference (km)50 50 50 50 50
SR loss/turn (GeV) 2.96 2.96 2.96 2.96 4.61
Ne/bunch (1012) 0.79 0.38 0.33 0.28 0.29
Bunch number 22 23 21 19 12
Beam current (mA)16.9 8.45 6.76 5.07 3.38
SR power /beam (MW)50 25 20 15 15.6
B0 (T) 0.065 0.065 0.065 0.065 0.1
Bending radius (km)6.2 6.2 6.2 6.2 3.98
Momentum compaction (10-4)
0.38 0.38 0.38 0.38 0.19
IP x/y (m)0.2/0.001 0.071/0.00048 0.056/0.00042 0.041/0.00035 0.07/0.000
35
Emittance x/y (nm)14.6/0.073 9.5/0.035 9.1/0.031 8.9/0.026 4.3/0.022
Transverse IP (um)54/0.27 25.9/0.13 22.7/0.11 19.2/0.096 17.3/0.087
x/IP 0.103 0.076 0.069 0.06 0.129
y/IP 0.103 0.103 0.103 0.103 0.129
VRF (GV) 6 6 6 6 6.6
f RF (MHz) 704 704 704 704 659
z (mm) 2.2 2.2 2.2 2.2 2.2
Energy spread (%) 0.13 0.13 0.13 0.13 0.16
Energy acceptance (%)5 5 5 5 5
BS (10-4) 13.8 13.8 13.8 13.8 16.3
n 0.6 0.6 0.6 0.6 0.7
BS (10-4) 4.3 4.3 4.3 4.3 5.9
Life time due to beamstrahlung (minute)
30 30 30 30 3
F (hour glass) 0.68 0.48 0.45 0.41 0.41
Lmax/IP (1034cm-2s-1)3.1 2.31 1.97 1.58 1.33
AC power/two beam (MW) *
286 143 114 86 89
Luminosity gain (%) 49 59 69 38
*
*y
y
L
Local compact FFS designL*=1.5m
IP parameters (25MW, 1.5m)
• IP parameters– BETX := 0.071;– ALFX := 0;– BETY := 0.00048;– ALFY := 0;– DX := 0;– DPX := -0.00795452718; – BLENG := 2.2E-3; !bunch length (m)– ESPRD := 1.3E-3; !energy spread (1)– EMITX := 9.5E-9;– EMITY := 0.035E-9;– D0->L = 1.5;
Refit IP to QF1• Fit five variables :
– QD0 length– QF1 length – Pole-tip strength of QD0– Pole-tip strength of QF1– Distance between QD0&QF1
Linear lattice• fit B1, B2 and B5 to obtain Dx=0 and Dpx=0 at exit of B5• reverse the system, refit QMs to match β and α.
Chromaticity
• natural chromaticity decreased (compared with L*=3.5m)
Reduce the length of Bend
• We are tring to reduce the length of the bends as the beam energy of CEPC is lower than the 500GeV ILC.
Local non-compact FFS design
Procedure & Method
• The CEPC design parameters :
two cases of βy=1mm and βy=0.35mm.
• FFADA program
• Matching section, CCS, Final Doublet.
• Non-interlaced sextupoles
Thanks to Hector and Rogelio for helping me setting up the FFADA program !
IP βy=1mm
at IP:bx=0.2 mby=1 mmL*=3.5 m
Beta Function at IP vs momentum
Good region of ±0.4% in Dp/p is necessary for the core in beam distribution.
IP lowβy=0.35mm
at IP:bx=0.041 mby=0.35 mmL*=3.5 m
Beta Function at IP vs momentum
Optical bandwidth needs optimization.
Conclusions and Prospects• For sub-mm βy* final focus design, chromatic effect is lar
ge, correction necessary.• For the local-compact FFS design, due to the large emitt
ance and low βy at IP, the high order aberration obvious, we tried to reduce the L* to reduce the chromatic aberrations.
Linear lattice design, reduce the bends, shorter length, MAPCLASS optimization for high order aberrations.
• For the local non-compact FFS design, using the non-interlaced sextupoles to reduce the third order “kick”, momentum bandwidth needs optimization.
Tracking beam size, MAPCLASS optimization for high order aberrations, momentum bandwidth optimization, Oide effect, error analysis…
Thank you !